BLEEDING BRAKE

1990 Chevrolet Truck

Tiny

joe1953

February, 17, 2014 AT 6:39 PM

I replace new wheel Cylinders on the rear and a use Master Cylinder the front Wheel brakes are Working but when I press the brake no fluid is going to the rear brake I took the brake fluid line loose at the rear to see will fluid come from it sometime a little fluid will come from the line most of the time it don't What could be the problem for the reason no fluid come out the line when press on the brake?

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Brake Fluid Bleeding

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Brake Bleed Issues

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Tiny

caradiodoc

February, 17, 2014 AT 7:02 PM

You put on a used master cylinder? No one is cheaper than me, but even I wouldn't do that. Almost certainly it was damaged when you bled the brakes. By the time a master cylinder gets to be about a year old, crud and corrosion build up in the bottoms of the bores the pistons ride in. You must never, ever push the brake pedal more than half way to the floor or you will run the lip seals over that crud and rip them. At that point you will either get no fluid or the pedal will slowly sink to the floor when you hold steady pressure on it.

Get a professionally-rebuilt master cylinder. You can buy rebuild kits too but they usually cost more than the rebuilt master cylinder. Plus, if you try to rebuild your own, you have to clean the bore completely, and there is a protective anodized coating on it to keep the aluminum from corroding. You can't do anything to scratch or remove that coating.

It IS okay to push the pedal to the floor when bleeding the system with a new master cylinder, but it's good practice to get used to not doing that. Don't forget to bench-bleed it first before you install it. Most rebuilt units come with the instructions and the hoses and fittings to do that.

Tiny

joe1953

February, 17, 2014 AT 7:31 PM

If it is the Master Cylinder Why do I have front brakes? When I press the brake pedal down it stop about 3 to 4 inches from the floor.

Tiny

caradiodoc

February, 17, 2014 AT 9:46 PM

All master cylinders since the late 1960s have two hydraulic systems. For older and rear-wheel-drive vehicles the front brakes are on one system and the rear brakes are on the other. That's why you have two steel lines connected to the master cylinder. Almost all front-wheel-drive cars use a "split-diagonal" system where the left front and right rear are on one system and the other two are on the other system.

When the brake pedal is run more than half way down to the floor, the chances of a lip seal being torn is probably 80 percent. Your front brake system survived so they still work.

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